Lecture Notes: Genetics and Guinea Pigs

Introduction

Discussed the concept of hairless guinea pigs.
Hairless guinea pigs are hard to find and likely wouldn't survive in the wild due to genetics.
The discussion focuses on genetics, DNA, and genes in the context of guinea pigs.

DNA and Genes: DNA makes up genes, and these are inherited from both mother and father.
Alleles: Forms of a gene, often represented by letters.
- Example: 'h' for hair.

Dominant Allele
- Represented by a capital letter (e.g., 'H').
- Dominant alleles will show up if present.
Recessive Allele
- Represented by a lowercase letter (e.g., 'h').
- Only shows up if there is no dominant allele present.

Genotype: The genetic makeup of an organism.
- Hairless guinea pig genotype: hh (homozygous recessive).
- Guinea pig with hair genotype: HH (homozygous dominant) or Hh (heterozygous).
Homozygous: Same alleles (e.g., HH or hh).
Heterozygous: Different alleles (e.g., Hh).
Phenotype: Physical traits of an organism (e.g., presence of hair).
- Phenotype ratio in offspring example: 3 have hair: 1 hairless.

Monohybrid Cross: Focuses on one trait.
- Example trait: presence of hair.
- Use of Punnett square to predict offspring traits.
Steps for a Monohybrid Cross:
1. Determine the genotypes of the parents.
  - Example: Both parents are heterozygous (Hh).
2. Place one parent's alleles across the top and the other's down the side of the Punnett square.
3. Fill in the Punnett square to predict offspring genotypes.
Results:
- Offspring genotypes: 1 HH, 2 Hh, 1 hh.
- Genotype ratio: 1:2:1.
- Percentage of genotypes: 25% HH, 50% Hh, 25% hh.
- Phenotype ratio: 3 have hair: 1 hairless.
- Phenotype percentage: 75% hair, 25% hairless.

They are predictive tools and represent probabilities, not certainties.
Real-life genetics can deviate from predictions due to the probabilistic nature.

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